cooling tower fills to optimize ct performanceindianpowerstations.org/ips 2013 presentations/day-1...

13/02/2013 ©2012 Brentwood Industries, Inc.

Cooling Tower Fills to Optimize

CT Performance Presented by Richard Aull, PE

Director of Engineering

Brentwood Industries

NTPC IPS 2013 O&M Conference

•Modern Fill Designs

•Fill Scaling & Fouling

•In-Situ Fouling Testing at Plant Bowen

•Case Studies

•Product Innovations

Presentation Summary


Modern Fill Designs


•Cooling tower fill should maximize heat transfer

but not at the expense of severe fouling.

•Selection is extremely dependent upon the

quality of make-up water.

•More frequently, poor quality water is being

utilized for plant make-up

Cooling Tower Fill


•Flute size (air & water flow pathways)

•Pathway configuration (cross-flutes,

offset-flutes, vertical-flutes)

•Surface features (micro-structure)

Factors That Influence Fill Performance


General Types of Counter-Flow Film Fill


Decreasing tendency to clog

Increasing performance

•The designed-in surface

features (micro-structure)

formed on the polymer fill

sheet

•Keeps the water film

mixed & turbulent for

maximum heat transfer

Film Fill Surface Structure


Surface

structure

enhances

air/water

contact

Film Fill Surface Structure


Cross Flute (CF)

Large specific

surface area

High performance

Poor anti-fouling

characteristics in

fouling waters

Good Poor

Fouling resistance in dirty

water systems

Thermal Performance

High-Efficiency Film Fill


High-Efficiency, Low-Fouling Film Fill

Offset Flutes (OF)

Large specific

surface area

High performance

Moderate anti-

fouling

characteristics

Good Poor


water systems

Thermal Performance


Anti-Fouling Film Fill

Vertical Flute (VF)

Lower specific

surface area

Moderate

performance

Excellent anti-fouling

characteristics

Good Poor


water systems

Thermal Performance


Fill for Severe Fouling Applications

Compact Droplet (Splash)

High droplet surface due

to integral drip points

Moderate performance

Excellent anti-fouling

characteristics

Integral Drip Points

Good Poor


water systems

Thermal Performance


High Performance Droplet Generating Fill

Droplet Formation video


Fill Scaling & Fouling


Scaling

•Scale is formed when the concentration of dissolved

solids (minerals) exceeds the solubility of that

particular scale-causing mineral

•When this situation occurs scale will form on any

surface in contact with the water in an untreated

cooling water system


Scaling

•Calcium and magnesium salts, are

more soluble in cold water than in

hot water

•Will form on heated surfaces

•Most other salts, including silica

are more soluble in hot water than

in cold water

•forms in low temperature areas,

as in the cooling tower fill


Causes of Fill Scaling

•Cycles of

Concentration too high

•Poor or fluctuating

water distribution

•Chemical treatment

upsets


Good Water Distribution is Key

•The nozzles must provide uniform and

continuous water entering all flutes of the fill

•If not, deposits will accumulate in poorly

wetted areas

•Forms an excellent base for biofilm growth

•Causes the accelerated accumulation of

both suspended solids & scaling minerals


Fouling of Fills

•Fouling is the deposition of materials that are

normally held in suspension in the cooling water such

as:

•Mud, silt, and other solids brought into the system with the

makeup water

•Dust, dirt, and debris scrubbed out of the air passing

through the tower

•Product leakage such as oils, corrosion products from the

system, and biological organisms, both living and dead


Causes of Fill Fouling

•High suspended solids

•High bacterial count

•High nutrient level

•Process contamination

•High concentrations of oils & grease


Examples of Fill Fouling


Fouling due to mud and silt accumulation

Biofilms

•Clusters of microorganisms adhering to surfaces

•Encased in an extracellular polysaccharide (glue) that they synthesize

• Found on surfaces in which sufficient moisture is present

•Develops rapidly in flowing systems where nutrients are available


Effect of Water Film Velocity on Biofilms


0

1

2

3

4

5

0 0.1 0.2 0.3 0.4 0.5 0.6

Bio

film

Th

ickn

ess

(mm

)

Mean Water Velocity (m/s)

Biofilm Accumulation*

*From Charackles, William G., “Biofilms”, 1990, John Wiley & Sons

Film Fill Design Strategy To Minimize Fouling

•Orient flutes vertically •Maximizes water film velocity

•Create large flute openings •Increases film velocity

•Reduces chance for airborne solids to accumulate

•19mm or larger

•Eliminate flute passage restrictions •Reduce crossover points


Water Film Velocities of Fills


0

0.05

0.1

0.15

0.2

0.25

0.3

CF-1900 OF-21ma VF-19Plus

Water Film Velocity

(m/s)

Results from Brentwood testing at 20 m3/hr/m2 water loading

In-Situ Fouling Testing

at Plant Bowen


In-Situ Fouling Testing at Plant Bowen


3500 Mw Coal Fired Power Plant

in southeastern USA

Tower for Unit 4

In-Situ Fouling Testing at Plant Bowen


Fill Test Beds

Test Packs Weighing Procedure


Test Results


40

50

60

70

80

90

100

110

0 50 100 150 200 250

Estimate of Performance Loss vs. Fouling

Pe

rfo

rma

nc

e L

os

s

(%)

Net Weight Gain (kg/m3) Source: CTI Technical Paper TP93-06, “Research of Fouling Film Fill”

Effect of Fill Fouling on Performance


Cross-Fluted Fill

Vertical-Fluted Fill

19mm

CF

21mm

OF

19mm

VF

25mm

Droplet

Allowed TSS w/good

microbial control (ppm):

<100

<200 <500 <1000

Allowed TSS w/poor

microbial control (ppm):

<25 <50

<200

<500

Allowed Oil & Grease

concentration (ppm)

None <1 <5 <50

Guidelines for Tower Fill Selection

‘Good’ biological control means oxidizing biocide supplied continuously with bactericidal residuals maintained, with total

aerobic bacteria (TAB) maximum plate counts not exceeding 100,000 cfu/ml.

‘Poor’ microbiological control implies little or no microbiological control or control subject to severe disruption, with

average TAB plate counts consistently over 100,000 cfu/ml. Other airborne contaminants should be considered also,

such as fine dust, dirt & debris.


Case Studies


Brentwood Products in 6 Cell FRP CF Tower


•Repacked tower serves a 250 MWe sub-bituminous coal

fired power plant in southwestern USA

•2,350m3 HTP-25 fill

•CTI 3rd party thermal test: Passed

Tri-States/Escalante Generating Station



LG&E/Trimble County Power Station

•New tower serves the new second unit of a 1,200 MWe coal

fired power plant in mid-central USA

•5,000m3 OF21ma fill

•3,350m2 CF80MAx drift eliminators


•CTI 3rd party drift test: 0.0004% (0.0005% contracted target)



•New tower serves a 520 MWe combined cycle power plant

in eastern USA

•3,425m3 OF21ma fill

•1,875m2 CF150MAx drift eliminators


Calpine/York Energy Center

Brentwood Products in Concrete ND Tower


•Repacked counterflow natural draft tower serves Units 3 & 4

of a 2,822 MWe coal fired power plant in southeastern USA

•18,000m3 VF19Plus fill

•Owner thermal test: Passed

Alabama Power/Miller Steam Plant

Product Innovations


Mechanically Assembled (MA) Fill

• Special tabs are

molded into the

individual fill sheets

• Pairs of sheets have

their tabs crimped

together


How MA Works


New ACCU-Shield Anti-Microbial

•Inhibits the growth of bacteria,

which contribute to fouling

•Environmentally safe both EPA

& FDA approved

•Not a coating, will not wear off

•Available for all fills & drift

eliminators


•ACCU-Shield recorded a 70%

reduction in weight gain

compared to the standard PVC

media after one year.

•Lower weight gain is from

reduced bio growth on the fill

which “sticks” airborne matter

and suspended solids to the fill

media

Weight Gain Comparison

Pack with ACCU-Shield vs. Control Pack without

ACCU-Shield

0.00

1.00

2.00

3.00

4.00

5.00

6.00

0 5 10 15 20

Months in Service

kg

/m3

ne

t w

eig

ht

ga

in

Pack w/ACCU-Shield

Pack w/Std PVC

New ACCU-Shield Anti-Microbial



Thank you for your attention!

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